As part of an attempt to establish a sustainable society, the production of eco-friendly biodegradable plastics is noted. Because poly(3-hydroxyalkanoic acid) (PHA) produced by microorganisms such as Ralstonia eutropha has both thermoplasticity and biodegradability, its applications as biodegradable plastics have been studied, with some already put in practical use.
Establishing a less costly production system and breeding microorganisms that can produce biodegradable plastics so as to show desired properties are important for wider use of biodegradable plastics. To achieve this, new types of biodegradable polyester synthases have been explored, enzyme production has been enhanced using genetic engineering methods, and metabolic engineering approaches have been applied to alter intracellular biosynthetic pathways.
For copolymer biodegradable plastics, for example, it is possible to control their physical properties by varying monomer ratios. However, no efficient method for modifying the monomer ratios of copolymers has been established, so biodegradable plastics with desired physical properties have not yet been obtained.